Seyfried starred alongside Meryl Streep, Pierce Brosnan and Colin Firth in the ABBA-themed film, which scored huge box office success with global takings of $573 million (£385 million).
Hollywood star Streep previously sparked gossip of a second installment, admitting she would be interested in signing up for another Mamma Mia! movie.
But Seyfried tells Moviehole.net, "I don't think that's correct. I don't think it's accurate. Because I don't see the point in trying to top something.
"I mean, maybe if they had a really good idea for a story, but I don't think they would do it to top the first one.
"It's a good movie. It's an original piece. It's something that was really popular on Broadway. It's a great soundtrack; a good, family-friendly movie."